Distance measuring apparatus



Oct. 25, 1949. E. L. GINZTQN DISTANCE MEASURING APPARATUS Orizinal Filed March l5. 1943 En wen L (im/z 70A/ ATTORNEY Patented Oct. 25, 1949 ms'rANcE l 1G APPARATUS Edward L. Ginzton, Garden City, N. Y., assigner to The Sperry Corporation, a corporation of Delaware original application Maren 1s, 194s, sensi No.

479,294. Divided and this application November u, 194s, semi No. soassi 3 Claims. (Cl. 343-13) This invention relates generally to the reilected-pulse type of radio systems, and the invention has reference more particularly to a novel distance-measuring system wherein pulses of electromagnetic energy are directed at a distant object and corresponding reiiected portions of this energy are received back'at the systexmnovel means being provided for determining the distance of the object.

This application is a division of copending application Serial No. 479,294, led March 15, 1943, in the names of William W. Hansen and Edward L. Ginzton.

An object of the present invention is to provide electronic means for and a method of obtaining as an electrical voltage signal a measure of the range or distance to an object in a reiiected-pulse type of object-detecting system.

Another object of the invention is to provide a distance-measuring, reiiected-pulse type radio system employing an electronic circuit for receiving infomation as to the time of transmission of a pulse and the time of receipt of the corresponding reiiected pulse, the said circuit operating from such information to compute and provide an output that is a direct voltage proportional to this lapse of time, and therefore proportional to the range or distance of the object.

Still another object of the present invention is to provide a novel distance-measuring system employing a pair of electron tubes ,so interconnected that one of said tubes only conducts during the interval of time between the transmitted and reflected pulses, thereby serving as a measure of the distance, the other of the said tubes being conductive when the first-mentioned tube is non conducting.

Still another object of the present invention is to provide a novel distance-measuring system wherein electronic means is provided for initiating flow of constant current in response to a Referring now to the figure, a radio sighting system I is provided which is preferably of the reiiected pulse type, as disclosed in copending application Serial No. 441,188, for "Radio gun control system," filed April 30, 1942, in the names of C. G. Holschuh et al. As described in that application, periodicV pulses of electromagnetic energy are radiated in a conical fashion about a distant object from a suitable reector schematically indicated at 2. I'he reflector 2 is also employed to receive back corresponding pulses reiiected from an object lying within the irradiated conical portion of space. The phase and magnitude of the variation in intensity of the reiiecting pulse may then be interpreted by suitable detecting circuits which produce output signal voltages proportional to the angular deviation in elevation and azimuth of the axis of the cone of space irradiated (the spin axis of reflector 2) with respect to the line of sight to the object.

These voltage signals may then be introduced into suitable servo mechanisms which operate to drive the spin axis of the reiiector 2 in such a direction as to reduce the signal voltages to zero. In this mannenthe spin axis is continuously maintained coincident with the line of sight to the object, thus providing a measure of the gular position of the target in elevation and azimuth. Azimuth and elevation output shafts (not shown) may be connected to the spin axis by suitable gearing so that the angular displacement of these shafts is then proportional to the present azimuth and elevation of the object.

VAs is well known, the lapse of time between a transmitted pulse and a corresponding received pulse is proportional to the distance to the object. The electronic circuit of Fig. "1 receives, as on leads 3 and 4, respectively, information as to the time of transmission of a pulse and the time of receipt ofthe corresponding reiiected pulse, and from this information operates to compute and provide across its output leads 5 and 6, a direct voltage proportional to this lapse of time, and, therefore, proportional to the slant range (Do) to theobject.

As shown, this electronic range measuring circuit essentially comprises two vacuum tubes 8 and 9 illustrated as triodes. The grid 8' of tube 8 is fed through the condenser I0 by the negative ltransmitted pulse received on lead 3. The grid 9' of tube 9 is fed through the condenser Il by the'negative reected pulse received on lead 4. Should the transmitted and reflected pulses appear in the radio sighting system only as positive pulses, it is a simple matter to provide reversaccuses responding negative pulses.

The plate supply voltage for both tubes, indicated as the battery I2. is .shown grounded at a point intermediate to its positive and negative terminals. The positive side of the battery is connected to the plate 8" oi' tube 8 through the resistor I8 and to the plate 8" of tube 8 through the resistor Il. The negative side of the battery is also connected to the plate of tube 8 through the resistors I8 and I8 and to the plate of tube 9 through the resistors I'I andv I8. The grid of tube 8 is connected to a point intermediate the resistors I1 and I8, while the grid of tube 8 is connectedrto a point intermediate the resistors I and I6. Tube 8 has its cathode 'I connected to the grounded output conductor 5. The cathode 1' of tube 9 is connected to the ungroundedoutput conductor 8 and then to ground through the resistor 2i. An integrating condenser 22 is connected in parallel 4with the resistor 2l, as shown.

It is apparent that the electron circuit for tube 8 is from ground, through the tube, through resistor I8, to the positive side of the battery I2 and back to ground. The circuit for tube 8 is Also, the battery I2 and Iresistors, I5, I6 and I3 constitute a closed circuit, and the battery I2 and resistors I1, I8 and I4 constitute a similar closed circuit.

' The theory of operation of the circuit is that because of the control influence exerted by the negative transmitted and reflected pulses applied to the grids of the two tubes, tube 8 only conducts during .the interval of time between the transmitted and reflected pulses. The condenser 22 functions to integrate or smooth out this tube current flowing through resistor 2I, thus providing a voltage across output conductors 5 and 6 which is proportional to the time interval during which tube 9 is conducting, and therefore, proportional to the slant range (Do) The circuit may be considered as having two conditions of stable operation, in the first of which tube 8 is conducting, and tube 9 is non-conducting, and in the second of which tube 9 is conducting and tube 8 is non-conducting. Transfer from the first to the second of these conditions of equilibrium is effected by the receipt of a negative transmitted pulse on the grid of tube 8, and retransfer is effected by the receipt of a negative reflected pulse on the grid of tube 8. In order to explain the operation, it will first be assumed that tube 8 is conducting and tube 8 non-conducting. The resulting current flow through resistor I8 lowers the potential of the point 28 to such an extent that the grid of tube 9 is maintained below cut-off, blocking current flow through tube 8. A negative transmitted pulse impressed upon the grid of tube 8 momentarily biases this tube beyond cut-off blocking current flow through tube 8. The resulting decrease of current through resistor I3 raises the potential of points 23 and 24, and therefore, of the grid of tube 8 to such a value that tube 9 begins to conduct. y

With'tube 9 conducting, the additional flow of plate current through resistor I4 causes a lowering of the potential of points 25 and 2S, and the grid of tube 8 is, therefore, maintained at a potential below cut-od. Accordingly, when the negative transmitted pulse has passed. tube 8 is prevented from conducting again and the circuit is operating under its second condition of equilibrium wherein tube 9 alone conducts. Tube 8 will continue to conduct until a negative reflected pulse is impressed upon its grid at which time current flow will be transferred to tube 8 in a manner exactly similar to the above described transfer of current flow to tube 8.

It will be obvious, therefore, that tube 8 will be conducting only for the time elapsing .between the receipt of a transmitted pulse on the grid of tube 8 and the receipt of a reflected pulse on the grid of tube 8. As previously stated, the parallel circuit consisting of resistor 2i and condenser 22 serves to measure the total current flow through tube 9 and to provide a voltage across the output conductors 5 and 6 winch is proportional to this total current flow, and therefore, also proportional to slant range (Do) Although direct current voltage signals have been employed throughout for the purpose of illustration, it will be apparent that many of the principles embodied in the present invention could obviously be employed to operate in a simllar manner on alternate current voltage signals.

It is therefore to be understood the present invention is not intended to be limited to the use of direct current voltage signals only.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In a reflected pulse type radio system, wherein periodic pulses of electromagnetic energy are directed at a distant object and the corresponding reflected portions of said energy pulses are received back at the system, means for deter mining the distance to said object, comprising an electronic circuit arrangement adapted to receive said transmitted and said received pulses, said circuit arrangement comprising a pair of electron tubes having their anodes and grids respectively interconnected, fixed bias means for the grids of said tubes connected independently of the gridplate interconnection, said circuit arrangement -having two modes of stable operation respectively initiated by said pulses, and means for producing a voltage proportional to the duration of that mode initiated by said transmitted pulses.

2. In a reflected pulse type radio system, wherein periodic pulses of electromagnetic energy are directed at a distant object and the corresponding reflected portions of said energy pulses are received back at the system, means for determining the distance to said object, comprising an electronic circuit arrangement including two electron =`tubes and associated circuit elements, said circuit arrangement having feedback means producing two modes of stable operation in the first of which only the rst of said tubes is conducting and in the second of which only the second of said tubes is conducting, means for applying a fixed normal bias on the grids of said tubes independently of said feedback means, means for impressing negative transmitted pulses upon the grid of the second of said tubes to initiate the first of said modes, means for impressing negative received pulses upon the first of said tubes to initiate the second of said modes,

a parallel resistor-capacitor circuit in series with the cathode of said iirst tube, and means for extracting the voltage across said parallel circuit.

3. In a reected pulse type radio system, wherein periodic pulses of electromagnetic energy are directed at a distant object and the corresponding reflected portions of said energy pulses are received back at the system, means for determining the distance to said object, comprising an electron tube, means for supplying a xed bias for the control electrode of said tube, means comprising a connection independent of said fixed bias means for initiating current flow through said tube upon the receipt of a negative transmitted pulse, means for terminating said current Ilow upon the receipt of a negative received pulse, a. resistor-capacitor parallel circuit arrangement in series with said tube, and means for extracting the voltage built up across said circuit arrangement.

EDWARD L. GINZTON.

BEFERIINCES CITED The following references are of record in the ille of this patent:

UNITED STATES PA'I'ENTS Number Name Date 2,055,883 Terry -Y Sept. 29, 1936 5 2,189,549 Hershberger Feb. 6, 1940 2,244,369 Martin June 3, 1941 2,266,509 Percival et al. Dec. 16, 1941 2,301,195 Bradford Nov. 10, 1942 2,324,797 Norton July 20, 1943 lo 2,337,328 Hathaway Dec. 21, 1943 2,416,333 Lehmann Feb. 25, 1947 2,421,018 De Rosa. May 27, 1947 2,426,454 Johnson Aug. 26, 1947 FGREIGN PATENTS 15 Number Country Date 497,147 Great Britain Dec. 9, 1938 469,417 Great Britain July 26, 1937 OTHER REFERENCES 

